The present invention relates to a data transmission apparatus for transmitting data and a method of the same, more particularly relates to a data transmission apparatus which suitably manages an encoding key and a decoding key used where a large amount of data is encoded and transferred and a method of the same.
Conventionally, in a TV broadcast or other data distribution service using a communications satellite, the flow of data was made in only one direction, that is, from the data distributor to the user. In recent years, since the transmission of digital data using communications satellite has becomes possible, transmission using the communications satellites has started for not only analog video and audio data such as TVS and movies, but also the text utilized in computers and digital video and audio data.
Here, conventional data distribution services using communications satellites such as TV broadcasting has been of the form with data distributed by a data distributor being simultaneously received and used by a large number of users. Contrary to this, where the digital data used in computers is distributed via a communications satellite, a function for distributing the data from the data distributor to a single or a plurality of users is required.
In the conventional transmission system using a communications satellite, however, there is a problem in that since the distribution is performed for analog data and since the data distribution is performed in only one direction from the data distributor to the user. Since no function for checking the errors in transmission is provided, the reliability of the data transmission is low. In the distribution of digital data, if even one bit of error is caused in the data due by the transmission, the received data no longer has any meaning.
In order to distribute such digital computer data by a wireless system with a high quality, it is necessary to secure a communication path for not only the distribution of data in one direction from the data distributor to the user, but also a communication path from the user to the data distributor. The conventional transmission system is not provided with such a function.
Also, in the conventional simultaneous communication or broadcast system from a data distributor to many users, all users always receive, use, or view the same information. There is no personal identification information of the system users, therefore it is not possible to distribute data from the data distributor to only specific users.
Further, where data is transmitted or a conversation is conducted by using a public telephone line, dedicated line, etc., in order to prevent the leakage of the transmitted information or maintain the reliability of the information against attack (interference) with respect to the transmitted information, plain text data is encoded (scrambled) and then transmitted, and the encoded data is decoded (descrambled) at the destination of reception. As a typical encoding system, a common key encoding system and a public key system have been known.
The common key encoding system is also referred to as the symmetrical encoding system. An algorithm private type and an algorithm public type have been known. As a typical algorithm public type, the DES (data encryption standard) has been known.
In the public key system, since an enormous amount of calculation is necessary for deriving the generated key from an inspection key, the generated key is not substantially decoded, therefore it is an encoding system wherein the encoding key can be made public and is referred to also as the asymmetrical key encoding system.
The encoding system is determined in accordance with the type of the line system through which the transmission data is transmitted, the degree of secrecy (secret) of the transmitted data, the amount of transmitted data, etc.
In data transmission using a dedicated line, the degree of leakage of the information and the attack of the transmitted data is low. But when data is transmitted by using a public telephone line, the degree of the leakage of information and the degree of attack becomes high. Further, the transmission of data using a satellite broadcasting line can be received by many unspecified apparatuses, therefore the degree of leakage of information becomes even higher.
FIG. 1 is a schematic structural view of an example of an encoded data transmitting apparatus for encoding the data on the transmission line by a common key encoding system.
In the encoded data transmitting apparatus of FIG. 1, reference numeral 101 denotes a transmitting apparatus (transmitter), reference numeral 102 denotes a receiving apparatus (receiver), 103 denotes a tapping apparatus (tapper), reference numeral 104 denotes a data transmission line, reference numeral 105 denotes data which should be transmitted, reference numeral 106 denotes an encoding unit provided in the transmitting apparatus 101, reference numeral 107 denotes an encoding key (encoding session key) used for the encoding in the encoding unit 106, reference numeral 108 denotes a decoding key (decoding session key), reference numeral 109 denotes a decoder for decoding the encoded data received from the data transmission line 104 using the decoding key, and reference numeral 110 denotes the data after decoding.
The transmitting apparatus 101, when transmitting the data 105 onto the transmission line 104, has the encoding unit 106 encode the data 105 by using the encoding key 107 and transmits the encoded data to the receiving apparatus 102 via the transmission line 104.
The receiving apparatus 102, when receiving the encoded data from the transmission line 104 (encoded data), has the decoder 109 decode the received encoded data by using the decoding key 108 corresponding to the encoding key 107 so as to obtain an intended decoded (deciphered) data 110.
In this example, even if the tapping apparatus 103 receives the encoded data from the transmission line 104 in the same way as the receiving apparatus 102, there is no decoding key 108, so it is difficult to correctly decode this. Namely, the tapping apparatus 108 ends up handling encoded (scrambled) data as is, therefore, in actuality, the information is prevented from being leaked to the tapping apparatus 103 side.
In a principal encoding system of the common key encoding system in this example, generally the encoding key 107 and the decoding key 108 have the same bit train.
Recently, broadcasters have been making satellite broadcasts for providing TV programs to only specific contractors. The transmission system used for the satellite broadcast can transmit a large amount of data (information) such as a video and audio in a short time. Further, a transmission system using a satellite can transmit a large amount of information in a short time and therefore is not limited to broadcastsxe2x80x94it has been widely utilized for the transmission of data such as computer data.
In transmission using a satellite, however, unlike a one-to-one communication system such as a telephone line and dedicated line, many unspecified receivers can easily receive the data (by receiving apparatuses), so it is easy to be tapped by nature. As a result, there is a high possibility that for example a pay satellite broadcast will be tapped. Therefore, it has been proposed too to also encode the video data and audio data of a TV broadcast for transmission.
In actual transmission, the encoding is not carried out for all data, but the data which should be encoded is encoded and transmitted onto the transmission line in accordance with the content of the data to be transmitted in the transmitting apparatus (for example, whether it is pay data or not). The receiver decodes all or part of the encoded data to determine whether or not the all or partially decoded data is necessary for it at the present by the information obtained as a result of this.
In the encoded data transmitting apparatus for transmitting encoded data in this way, it is necessary for the transmission side and reception side to hold the encoding key and decoding key in advance in secret so as not to be known to third parties.
As in the conventional method where the transmission side holds the encoding key and the reception side holds the decoding key, for example, when encoding and transmitting video data etc. by using for example a satellite transmission line, consideration may be made of the method of the transmitter sending the receiver a piece of paper, an IC card, etc. on which the decoding key is recorded by the mail or another method, the method of transmitting the encoding key and the decoding key through the same transmission line as the satellite transmission line for sending the video data (satellite transmission line), and further a method combining them.
In the conventional method of management of an encoding key and decoding key, there are the following problems.
A first problem is related to how the transmitter gets to hold the encoding key or how the receiver gets to hold the decoding key or.
As explained above, as the method for having the encoding key held by the transmitter and having the decoding key held by the receiver, the method for sending an object such as the paper and IC card on which the decoding key is recorded from the transmitter to the receiver by the method of mail, etc., the method of sending the same by the satellite transmission line, and further the method combining them, are general.
(1) In the method of sending an object on which the decoding key is recorded through the mail etc., due to the trouble of the procedure thereof, it is not easy to change the encoding key and the decoding key. This means that a large amount of data encoded using the same key will be transmitted onto the transmission line and that, since a large amount of information will be given to the tapper, the safety with respect to the deciphering will be low.
(2) In the method of sending the decoding key by using a satellite transmission line, the data on the satellite transmission line will be received by many unspecified persons having the antennas and other equipment irrespective of whether or not the transmitter desires these persons as the receivers. Thus, there is a possibility that the decoding key will be learned by persons other than the receivers expected by the transmitter and therefore there is problem that the safety of the transmission cannot be held.
(3) In the method combining the above two methods, that is, the method of preparing the decoding key from information recorded on an object sent by mail etc. and information transmitted through a satellite transmission line, the drawbacks of the two methods are compensated and the safeness of the transmission method becomes higher to a certain extent. However, the problem that information for a decoding key sent through the mail etc. cannot be easily changed due to the troublesomeness of the procedures and the problem that the information for a decoding key transmitted through a satellite transmission line ends up being received by a large number of unspecified persons not desired by the transmitter remain.
A second problem relates to how to decide whether or not the transmitter has encoded the data or how the receiver should decode the received data.
As mentioned above, in the methods which are used in general at the present, the transmitting apparatus views the contents of the data, encodes the data which must be encoded, and transmits it onto the transmission line. The receiving apparatus decides whether or not this data is necessary for it by the information obtained by decoding all or part of the encoded data received from the transmission line. In this method, however, the transmitting apparatus has to perform processing for learning the contents of the data for determining whether or not the data must be encoded. Further, the receiving apparatus has to determine whether the received encoded data is required by it or not, that is, it has to perform processing for decoding all or part of the encoded data for deciding whether or not the data is addressed to it. For this reason, while it is necessary to perform the transmission at a higher speed and perform the processing in the apparatuses, with the hardware configuration heretofore, such a demand could not be satisfied.
An object of the present invention is to enable effective encoding of transmitted data at the transmitting side and effective decoding of the encoded data transmitted at the receiving side.
Another object of the present invention is to enable transmission of digital data by a wireless method without causing errors in transmission.
Still another object of the present invention is to enable transmission of digital data by a wireless method from a transmitting apparatus to just specific clients.
According to the present invention, there is provided a data transmitting apparatus connected to a first transmission system and a second transmission system, the data transmitting apparatus having a key transmitting means for transmitting through the second transmission system decoding key information for decoding encoded data sent through the first transmission system, generating means for adding first transmission control information to the data to be encoded and transmitted so as to generate transmitted data, encoding means for generating encoded data from the transmitted data based on encoding key information corresponding to the decoding key information, and data transmitting means for transmitting to the first transmission system the encoded data generated by the encoding means.
Preferably, the communication capacity per unit time of the first transmission system is larger than the communication capacity per unit time of the second transmission system. Specifically, the first transmission system includes a satellite transmission line and the second transmission system includes a cable transmission line.
Preferably, the key transmitting means transmits destination information of the transmitted data along with the decoding key information through the second transmission system.
More preferably, the key transmitting means transmits the same decoding key information and destination information to a plurality of receiving apparatuses connected to the first transmission line and the second transmission line.
Still more preferably, the encoding means generates encoded data from the transmitted data based on the encoding key information and the destination information of the transmitted data.
Preferably, further provision is made of a key encoding means for encoding the work key information to generate decoding key information.
Preferably, the encoding means generates encoded data from the transmitted data based on the work key information and the destination information of the transmitted data.
Preferably, the first transmission control information includes the destination information of the transmitted data.
Preferably, the first transmission control information includes an address defined by an Internet protocol as the destination information.
Preferably, the encoding means encodes the transmitted data including the first transmission control information.
Preferably, the encoding means adds to the transmitted data second transmission control information including the same destination information as the destination information included in the first transmission control information to generate the encoded data.
Preferably, the encoding means adds a CRC check bit to generate the encoded data.
Preferably, the second transmission control information includes information indicating the presence of coding of the data to be transmitted.
Preferably, the second transmission control information includes information for distinguishing whether the data to be transmitted is information responding to a request from a receiving apparatus or whether it is control information for operating the communications system including the data transmitting apparatus.
Further, according to the present invention, there is provided a data transmitting apparatus connected to a first transmission system and a second transmission system, the data transmitting apparatus provided with a key receiving means for receiving from the second transmission system encoding key information for encoding encoded data transmitted through the first transmission system, data generating means for adding control information to the data to be encoded and transmitted to generate transmitted data, encoding means for generating encoded data from the transmitted data based on the encoding key information, and data transmitting means for transmitting through the first transmission system the encoded data generated by the encoding means.
Preferably, the encoding means is provided with key decoding means for decoding the encoding key information to generate work key information and uses the work key information decoded by the key decoding means to generate encoded data.
More preferably, the encoding means generates encoded data based on the work key information and the destination information of the encoded data.
Further, according to the present invention, there is provided a data transmission method for transmitting data using a first transmission system and a second transmission system, the data transmission method comprising a key transmitting step for transmitting through the second transmission system decoding key information for decoding encoded data transmitted through the first transmission system, a data generating step for adding first transmission control information to the data to be encoded and transmitted to generate transmitted data, an encoding step for generating encoded data from the generate transmitted data based on encoding key information corresponding to the decoding key information, and a data transmitting step for transmitting the encoded data generated by the encoding step through the first transmission system.
Preferably, the key transmitting step transmits destination information of the transmitted data along with the decoding key information through the second transmission system.
More preferably, the key transmitting step transmits the same decoding key information and destination information to a plurality of receiving apparatuses connected to the first transmission line and the second transmission line.
Still more preferably, the encoding step generates encoded data from the transmitted data based on the encoding key information and the destination information of the transmitted data.
Preferably, further provision is made of a key encoding step for encoding the work key information to generate decoding key information.
Preferably the encoding step generates encoded data from the transmitted data based on the work key information and the destination information of the transmitted data.
Preferably, the first transmission control information includes the destination information of the transmitted data.
Preferably, the first transmission control information includes an address defined by an Internet protocol as the destination information.
Preferably, the encoding step encodes the transmitted data including the first transmission control information.
Preferably, the encoding step adds to the transmitted data second transmission control information including the same destination information as the destination information included in the first transmission control information to generate the encoded data.
Preferably, the encoding step adds a CRC check bit to generate the encoded data.
Preferably, the second transmission control information includes information indicating the presence of coding of the data to be transmitted.
Preferably, the second transmission control information includes information for distinguishing whether the data to be transmitted is information responding to a request from a receiving apparatus or whether it is control information for operating the communications system including the data transmitting apparatus.
Further, according to the present invention, there is provided a data transmission method in a transmitting apparatus connected to a first transmission system and a second transmission system, the data transmission method comprising a key receiving step for receiving from the second transmission system encoding key information for encoding encoded data transmitted through the first transmission system, data generating step for adding control information to the data to be encoded and transmitted to generate transmitted data, an encoding step for generating encoded data from the transmitted data based on the encoding key information, and a data transmitting step for transmitting through the first transmission system the encoded data generated by the encoding step.
Preferably, the encoding step is provided with a key decoding step for decoding the encoding key information to generate work key information and uses the work key information decoded by the key decoding step to generate encoded data.
More preferably, the encoding step generates encoded data based on the work key information and the destination information of the encoded data.
Further, according to the present invention, there is provided a data receiving apparatus connected to a first transmission system over which encoded data is transmitted and a second transmission system over which key information is transmitted, the data receiving apparatus provided with key receiving means for receiving from the second transmission system decoding key information for decoding encoded data received from the first transmission system, a data receiving means for receiving the decoded data from the first transmission system, a data restoring means for deleting first transmission control information from the encoded data, and a decoding means for decoding the encoded data from which the first transmission control information was deleted based on the decoding key information to generate decoded data.
Preferably, the communication capacity per unit time of the first transmission system is larger than the communication capacity per unit time of the second transmission system. Specifically, the first transmission system includes a satellite transmission line and the second transmission system includes a cable transmission line.
Preferably, the key receiving means receives destination information of the encoded data along with the decoding key information from the second transmission system.
More preferably, a plurality of receiving apparatuses are connected to the first transmission system, and the key receiving means receives the same decoding key information and destination information as other receiving apparatuses connected to the first transmission line and the second transmission line.
Preferably, the decoding means generates decoded data from the received data based on the decoding key information and the destination information of the encoded data.
Preferably, the decoding means is provided with key decoding means for decoding the decoding key information to generate work key information and uses the work key information generated by the key decoding means to decode the encoded data.
Preferably, the decoding means decodes the encoded data based on the work key information and the destination information of the encoded data.
More preferably, the first transmission control information includes the destination information of the encoded data.
Still more preferably, the first transmission control information includes an address defined by an Internet protocol as the destination information.
Specifically, the decoding means decodes the encoded data which was encoded including the first transmission control information.
Preferably, further provision is made of a judgement means for judging if the encoded data is directed to itself based on the second transmission control information including the same destination information as the destination information included in the first transmission control information of the encoded data.
Preferably, the judgement means judges if the encoded data is directed to itself and checks to the CRC check bit added to the encoded data to check for errors.
More preferably, the judgement means judges if the encoded data is directed to itself and decides whether to decode or not based on the information indicating the presence of encoding included in the second transmission control information.
Preferably, the second transmission control information includes information for distinguishing whether the received data is information responding to a request from its own receiving apparatus or whether it is control information for operating the communications system including the receiving apparatus.
Further, according to the present invention, there is provided a data receiving apparatus connected to a first transmission system and a second transmission system, the data receiving apparatus provided with a key transmitting means for transmitting through the second transmission system encoding key information for preparing encoded data received from the first transmission system, data receiving means for receiving the encoded data encoded based on the encoding key information from the first transmission system, data restoring means for deleting the first transmission control information from the encoded data, and a decoding means for decoding the encoded data based on decoding key information corresponding to the encoding key information.
Preferably, further provision is made of a key encoding means for encoding work key information to generate encoding key information.
More preferably, the decoding means is provided with a decoding key generating means for generating a decoding key based on the work key information and the destination information of the encoded data and decodes the encoded data based on the decoding key generated by the decoding key generating means.
Further, according to the present invention, there is provided a data receiving method in a receiving apparatus connected to a first transmission system and a second transmission system, the data receiving method comprising a key receiving step for receiving from the second transmission system decoding key information for decoding encoded data received from the first transmission system, a data receiving step for receiving the decoded data from the first transmission system, a data restoring step for deleting first transmission control information from the encoded data, and a decoding step for decoding the encoded data from which the first transmission control information was deleted based on the decoding key information to generate decoded data.
Preferably, the key receiving step receives the same decoding key information and destination information as other receiving apparatuses connected to the first transmission system and the second transmission system.
More preferably, the decoding step generates decoded data from the encoded data based on the decoding key information and the destination information of the encoded data.
More preferably, the decoding step is provided with key decoding step for decoding the decoding key information to generate work key information and uses the work key information generated by the key decoding step to decode the encoded data.
Preferably, the decoding step decodes the encoded data based on the work key information and the destination information of the encoded data.
Preferably, the first transmission control information includes the destination information of the encoded data.
More preferably, the first transmission control information includes an address defined by an Internet protocol as the destination information.
Preferably, the decoding step decodes the encoded data which was encoded including the first transmission control information.
Preferably, further provision is made of a judgement step for judging if the encoded data is directed to itself based on the second transmission control information including the same destination information as the destination information included in the first transmission control information of the encoded data.
Preferably, the judgement step judges if the encoded data is directed to itself and checks to the CRC check bit added to the encoded data to check for errors.
More preferably, the judgement step judges if the encoded data is directed to itself and decides whether to decode or not based on the information indicating the presence of encoding included in the second transmission control information.
Preferably, the second transmission control information includes information for distinguishing whether the received data is information responding to a request from its own receiving apparatus or whether it is control information for operating the communications system including the receiving apparatus.
Further, according to the present invention, there is provided a data receiving method in a receiving apparatus connected to a first transmission system and a second transmission system, the data receiving method comprising a key transmitting step for transmitting through the second transmission system encoding key information for preparing encoded data received from the first transmission system, a data receiving step for receiving the encoded data encoded based on the encoding key information from the first transmission system, a data restoring step for deleting the first transmission control information from the encoded data, and a decoding step for decoding the encoded data based on decoding key information corresponding to the encoding key information.
Preferably, further provision is made of a key encoding step for encoding work key information to generate encoding key information.
Preferably, the decoding step is provided with a decoding key generating step for generating decoding key information based on the work key information and the destination information of the encoded data and decodes the encoded data based on the decoding key generated by the decoding key generating step.
Further, according to the present invention, there is provided a data transmission apparatus having a first transmission system and a second transmission system, the data transmission apparatus provided with:
a transmitting apparatus having a key transmitting means for transmitting through the second transmission system decoding key information for decoding the encoded data transmitted through the first transmission system, data generating means for generating transmitted data added with first transmission control information from the data to be encoded and transmitted, encoding means for generating encoded data from the transmitted data based on encoding key information corresponding to the decoding key information, and data transmitting means for transmitting through the first transmission system the encoded data generated by the encoding means and
a receiving apparatus having a key receiving means for receiving from the second transmission system decoding key information for decoding the encoded data received from the first transmission system, data receiving means for receiving the encoded data from the first transmission system, data restoring means for deleting first transmission control information from the encoded data, and decoding means for decoding the encoded data based on the decoding key information.
Further, according to the present invention, there is provided a data transmission apparatus having a first transmission system and a second transmission system, the data transmission apparatus provided with:
a transmitting apparatus having a key receiving means for receiving from the second transmission system encoding key information for encoding the encoded data transmitted through the first transmission system, data generating means for generating transmitted data added with control information from the data to be encoded and transmitted, encoding means for generating encoded data from the transmitted data based on encoding key information, and data transmitting means for transmitting through the first transmission system the encoded data generated by the encoding means and
a receiving apparatus having a key transmitting means for transmitting through the second transmission system encoding key information for preparing the encoded data received from the first transmission system, data receiving means for receiving the encoded data encoded based on the encoding key information from the first transmission system, data restoring means for deleting first transmission control information from the encoded data, and decoding means for decoding the encoded data based on decoding key information corresponding to the encoding key information.
Further, according to the present invention there is provided
a data transmission method using a transmission apparatus having a first transmission system and a second transmission system, the data transmission method comprising:
a transmitting processing step having a key transmitting step for transmitting through the second transmission system decoding key information for decoding the encoded data transmitted through the first transmission system, a data generating step for generating transmitted data added with first transmission control information from the data to be encoded and transmitted, an encoding step for generating encoded data from the transmitted data based on encoding key information corresponding to the decoding key information, and a data transmitting step for transmitting through the first transmission system the encoded data generated by the encoding step and
a receiving processing step having a key receiving step for receiving from the second transmission system decoding key information for decoding the encoded data received from the first transmission system, a data receiving step for receiving the encoded data from the first transmission system, a data restoring step for deleting first transmission control information from the encoded data, and a decoding step for decoding the encoded data based on the decoding key information.
Further, according to the present invention, there is provided a data transmission method for transmission of data using a transmission apparatus having a first transmission system and a second transmission system, the data transmission method comprising:
a transmitting processing step having a key receiving step for receiving from the second transmission system encoding key information for encoding the encoded data transmitted through the first transmission system, a data generating step for generating transmitted data added with control information from the data to be encoded and transmitted, an encoding step for generating encoded data from the transmitted data based on encoding key information, and a data transmitting step for transmitting through the first transmission system the encoded data generated by the encoding step and
a receiving processing step having a key transmitting step for transmitting through the second transmission system encoding key information for preparing the encoded data received from the first transmission system, a data receiving step for receiving the encoded data encoded based on the encoding key information from the first transmission system, a data restoring step for deleting first transmission control information from the encoded data, and a decoding step for decoding the encoded data based on decoding key information corresponding to the encoding key information.